Mixing pipette



June 1958 J. F. RYLEY 2,836,979

MIXING PIPETTE Filed April 5, 1955 12 I07 15 aa 1: o

INVENTOR ATTQ EYS United States Patent MIXING PIPETTE James F. Ryley, Toledo, Ohio, assignor to Owens-Illinois Glass Company, a corporation of Ohio 7 Application April 5, 1955, Serial No. 499,455

3 Claims. (Cl. 73425.4)

The present invention relates to pipettes and more particularly to mixing pipettes formed of glass or other suitable material used for clinical blood analyses. This invention provides an improved type of laboratory mixing pipette for diluting small portions of liquids.

These pipettes are small rod-like devices having upper and lower capillary tubes with an enlarged bubble or mixing chamber arranged between the two tubes. The enlarged chamber has a considerably greater internal diameter than the internal diameter of the capillary tubes and is commonly referred to as a mixing ampulla. This invention provides an improved and simplified type of mixing pipette having a mixing ampulla constructed with one or more baflles therein to more uniformly mix several liquids.

Pipettes of the subject type or chiefly employed in blood count determinations of human blood to indicate the relative proportions of red and white corpuscles pres ent in a given blood specimen. Also such pipettes are used in other laboratory determinations such as the detection of human disease.

The subject pipettes are employed to dilute in accurate proportions small quantities of liquids, usually the liquid to be analyzed being diluted by a suitable diluent to prepare a solution for examination. In determining blood counts an accurately measured amount of a blood specimen is drawn into the graduated mixing pipette and diluted with an accurately measured amount of an appropriate diluting agent to destroy one type of blood corpuscle. Where a count of the red corpuscles is required the white are destroyed by selecting a suitable reagent, thus permitting a count of the red only. Conversely, to count the white, the red are destroyed by another type reagent leaving the white to be counted. The two liquids must be intimately mixed to achieve the destruction of the unwanted type corpuscle.

Most common pipettes of the mixing type have one or more freely movable, solid bodies located within their mixing chamber or ampulla. A loose body is provided in the ampulla in the form of a small bead or rod which serves as a stirrer when the pipette is rotated or shaken. The head or rod is usually a piece of glass larger than the capillary ports which can roll around within the ampulla to facilitate and hasten the admixing of the liquids. The pipette is agitated in such a manner as to move the mixing element through the contained liquids to obtain by the shearing forces produced uniformity and homogeneity in the mixed solution. The main disadvantage of such a mixing element is its tendency to lodge in the mouth of the small lower capillary tube to retard the flow of the solution therefrom. Other pipettes have movable mixing elements attached to the internal sidewalls of the ampulla, but both types of mixing chambers are relatively expensive to manufacture.

In the manufacture of such pipettes the normal procedure is to form the mixing ampulla by locally heating a portion of capillary tube of desired length having one end closed. When the glass in the heated portion has softened, internal pressure is then applied within the tube to expand the moldable portion to given dimensions to form the mixing chamber. Opening the mixing chamber of these pipettes to introduce the mixing element is a delicate manufacturing operation. The mixing chamber must either be opened by punching a hole therein or by severmg the chamber completely to introduce the element into the enclosed space. After the element is placed therein, the hole must be plugged or the halves joined by fusing the glass together. Such pipettes are costly to manufacture requiring fabrication by skilled hands in individual operations.

The principal object of the present invention is to provide a mixing pipette for blood diluting analyses of improved and simplified construction which will properly mix small quantities of liquids by improved flow patterns and which can be economically manufactured with its mixing chamber formed in one operation.

Another object of this invention is to furnish a pipette having a mixing chamber which will remain open at the capillary ports to permit uniform introduction and discharge of the contained liquids.

Another object of the present invention is to provide a pipette having a mixing chamber of such surface contour that sufiicient turbulence is created within the contained liquids on agitation to thoroughly unite the said liquids.

Another object of this invention is to provide a diluting pipette for mixing small amounts of liquids in which the mixing is not dependent on agitation or shaking alone, but one in which contoured surfaces are provided in the mixing chamber to create turbulence in the liquids when the same are drawn into and removed from the chamber.

Another object of this invention is to provide a pipette which can be easily and efiiciently cleaned after use by flushing the interior with another liquid and similarly agitating the same to scrub the inner surfaces by the turbulence created.

The specific nature of this invention, as well as other objects and advantages thereof, will become apparent to those skilled in the art from the following detailed description taken in conjunction with the annexed sheet of drawings, on which by way of preferred example only, is illustrated one embodiment of this invention.

Referring to the accompanying drawings:

Fig. l is an elevational view of a mixing pipette illustrating one embodiment of this invention;

Fig. 2 is an enlarged sectional view partly in elevation of a portion of Fig. 1 showing the mixing chamber in detail;

Fig. 3 is a sectional view taken on line 3-3 of Fig. 1; and

Fig. 4 is a sectional view similar to Fig. 3 showing a modification of the form of the mixing elements.

Referring to Fig. 1 illustrating the presently preferred embodiment of this invention, there is shown a pipette having a glass body of rod or tubular shape with a stem 10 comprising the major postion of its length. The stem 10 has an axial capillary bore or passageway 12 extending through its entire length which terminates at the outer stem end of the usually pointed tip 13. The other end of the capillary bore 12 opens into the inner mixing chamber or ampulla 14 which is an expanded space entirely closed except for two capillary openings or bores leading therefrom.

The enlarged chamber 14 is connected with a neck 15 of cross-sectional shape and size similar to the stem 10, at a position opposite to and in line with the longitudinal axis of the stem 10. The neck 15 may be shorter in length than the stem 10 and is formed with a similar axial capillary bore 16 opening into the mixing chamber 14 at its inner end. The outer end of the capillary bore 16 terminates at an -open end '17 of the neck '15 which generally has a rib (not shown) formed on its outer edge over which is attached a length of flexible rubber tubing 18. The rubbertubing 18; has a short length of glass tube-19 comprising amouthpice fitted in its other end 'ments or baflies 20 located therein; The baffies 20 are formed in the. sidewalls in fixed positions by pressing localized areas of the sidewalls inwardly. The bafiies'Zt are placed in such internal arrangement as to provide'tho optimum amount of mixing action when the liquids in the chamber 14 are subjected to agitation by shaking the pipette. The number of baflies 20 comprising the fixed mixing elements is determined by the most eflicient mix ing action which can be obtained with the minimum number of bafiies commensurate with efiicient and'economical manufacture. Although one bafiie .may sufiiee, two or more baffles 20 may be required to obtain the most satisfactory mixing of liquids with a minimum amount of agitation. The baffies 20 [consist of hollow; conical, tapered or similar shaped projections directed inward toward the longitudinal axis of the pipette perhaps with their axes substantially normal to said major axis as illustrated inFigs. 2 and 3. The baffles 29 may consist of tin-shaped fingers as illustrated in Fig. 4, substantially perpendicular to the longitudinal axis or at an angle thereto such as may produce a rotary motion when the liquids are drawn into the chamber and shaken.

The mixing elements or baffles 20 can be arranged uniformly spaced within the chamber or concentrated in any portion thereof. Many modifications may be resorted to both as to the specific form of and in positioning the baflies 20 depending'upon the properties of the specific liquids, to be mixed. The mixing chamber 14, being of substantially greater volume than the capillary bores holds the major portion of the liquids to be mixed. A certain amount of mixing is obtained as the liquids are drawn into the chamber. The shape and design of the baflles 2t) promote mixing as the liquids are drawn past and around the same.

' The pipette is usually calibrated over most of its length with volumetric. markings on the stern and neck por-' tionslS. Thecapillary bore 12 of the stemii) is usually fully calibratediwith markingson the external stem surface such as 0.5 to 1 and the neck 35 is partially calibrated p is obtained during the period of agitation.

, '4" f pipette is then shaken manually or mechanically for a brief period of time to unite the liquids to produce uni formity and homogeneity in the diluted solution. During this agitation the baflies create turbulence in the solution to uniformly disperse one liquid in the other. 7

The mixing elements or baiiies 24) being fixed present no opportunity for their interference with the flow of the liquids into or out of the chamber 14 as in the case of a loose mixing element. The liquidsare able to smoothly flow into the mixing chamber 14 and be mixed during their introduction by the fixed elements and able to be further mixed during their discharge after a short period of agitation. Of course the greatest amount of mixing Production of my invention is a simple matter; baffles 20 in the pipette may be formed by locally heating a part of the pipette and placing this heated portion in a special mold having protuberances or projections in its side walls to produce the baffles. The heated glass, in

moldable andblow'able form, is expanded within the mold by pneumatic pressure so that the chamber 14 is formed and simultaneously theglass forms about the projections of the mold to produce the baffles.

The desired shape and size of the baffles can be obtained by proper mold design. Forming the mixing .bafi'les' within the'chamber in one operation as the glass is expanded will permit more economical manufacturing of the subject pipette.

Various modifications maybe resorted to within'the 2. A mixing pipetteeomprising an upper capillarytube a lower capillary tube and a mixing chamber therebetween, the internal diameter ofthe walls of said chamber being in excess'of that of the internal diameter of said, tubes, and a'plurality of inwardly directed baflies formed as an integral part of the side walls of said mixing chamber.

3. A mixing pipette forclinical analysis comprising an upper capillary tube, a lower capillary tube and a mixing ampulla having curved sidewalls arranged between said upper and lower tubes, said ampulla having a plurality of tapering projections formed at irregular intervals along and in said curved sidewalls thereof, said projections being directed inwardly at anangle to the longitudinal axis of said pipette. r I

References Cited in the file of this patent STATES PATENTS 45,309 Bliss Dec. 6, 1,762,807 Arnold June 10, 1930 2,104,325 Jufia Jan. 4, 1938 2,238,174 Kelm Apr. 15,1941

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